This invention relates to an electronic musical instrument more particularly an electronic musical instrument, which is capable of successively varying the tone pitch of a generated musical tone, further capable of setting an arbitrary width of pitch variation.
As has been well known in the art, there has been proposed an electronic musical instrument wherein the tone pitch of the generated musical tone is gradually varied over a predetermined pitch variation width so as to provide such various effects regarding pitch variation as a glissando effect, a portamento effect and a pitch bender effect. Each of these portamento, glissando and pitch bender effects is obtained by controlling the tone pitch of the generated musical tone. More particularly, the glissando effect is obtained by stepwisely varying the tone pitch of the generated musical tone from one pitch to the other at a spacing of semitone, whereas the portamento effect is obtained by smoothly and continuously varying the tone pitch of the generated musical tone from one tone pitch to the other. The difference between the glissando effect and the portamento effect lies in that whether the width of pitch variation (amount of variation of the tone pitch per unit time) is equal to semitone or smaller than it. In other words, it may be considered that when the width of variation of the tone pitch of the glissando effect is made extremely small, a portamento effect is obtained. The pitch bender effect is obtained when the tone pitch of the generated musical tone is varied to other pitch above or below the nominal pitch in accordance with the amount of the operation of a operating member.
However, in the prior art electronic musical instrument since the variation of the tone pitch is limited to a spacing of semitone scale or to a smooth variation, the musical expression effect would also be limited.